1. Field of the Invention
The present invention relates to the field of portable electronic devices that contain display devices. More particularly, the present invention relates to devices that contain a touch screen assembly that is activated by finger touch or by stylus pressure.
2. Related Art
Digital display devices are found in numerous electronic products such as wrist watches, hand calculators, cell phones and Personal Digital Assistants (PDA). Flat panel touch screen displays are included in certain applications both to present information to the user as well as to accept input data by means of user touch screen commands. Such displays include a digitizer mechanism and a display mechanism. A typical digitizer mechanism consists of a digitizing element having a flexible film supported slightly above the surface of the digitizing element. A pressure applied to the outer surface of the flexible film that causes the film to deflect and contact the digitizing element at a point can be used as an input signal to activate the digitizer mechanism.
The flexible film and the digitizing element must be mounted in a support housing to provide and maintain the proper spacing between the two. At the same time, additional protection against moisture, dust and mechanical damage must be provided for the flexible film used in the digitizer mechanism. Thus, an additional outer protective film mounted above the digitizer flexible film is generally included in the touch screen display assembly. The problem here is the reduction in sensitivity to the external mechanical pressure required to activate the digitizer mechanism. In addition, the added film may increase overall opacity which makes it more difficult to view any display element housed within.
Typically, a touch screen mechanism and a display mechanism are mounted within an enclosure in a recessed fashion. That is, the surface of the additional protective film which actually forms the outermost surface of the digitizer mechanism is on a level below the outer edges of the supporting enclosure which acts as a bezel. The resulting product then has a rim or step-down edge surrounding the touch screen which presents the typical bezel-like appearance. One problem with the bezel design is maintaining a moisture and dust free environment for the touch screen mechanism is made difficult. Such an assembly often does not provide a satisfactory moisture and dust proof enclosure. An additional problem involves the complexity and cost of assembly. Yet another problem involves the overall thickness of the device. The bezel design adds unwanted thickness to the display components.